CELL CHEMISTRY

There are three types of substances that life is dependent on. These are carbohydrates, proteins, and lipids (fats).                                                                                                                                                      

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1. Carbohydrates: These are used to produce energy for cellular activities.                                          

Types of carbohydrates:                                                                                                                            (a) simple sugars (monosaccharides): One sugar molecule–  Examples: Glucose, fructose and galactose.            

                               

(b) disaccharides: Two monosaccharide joined together.                  

Examples: Lactose = glucose + galactose; Sucrose = glucose + fructose; Maltose = glucose + glucose 

   

Exam hints: Memorize what the disaccharides are composed of.  In order words, what are the end products if you break down or digest a disaccharide.

                                                                                

(c) Complex sugars: Starch, cellulose and glycogen are made up of so many glucose joined together.

Exam hints: Glycogen is the storage form of carbohydrate in animals only . Cellulose is only found in plant cells.

2. Proteins are made up of amino acids. Proteins are the structural building blocks of the organism.

3. Lipids (Fats and oil) are made up of fatty acids and glycerol.

Test for some food substances:

Type of food substance	Test
Starch	Iodine test: Turns blue-black
Simple sugar (Glucose)	(a) Benedicts test: Brick-red coloration (b) Fehlings test: brick red coloration
Protein	Biuret test: light-blue color becomes purple
Lipid	Paper test: Oil stains paper

Exam hints: Memorize the test for the food substances.